Backlash take-up device



Sept. 16, 1952 RQKQS 2,610,519

BACKLASH TAKE-UP DEVICE Filed Sept. 8, 1951 MCHAEL PE kKOQ PatentedSept. 16, 1952 Michael; Pl Bloko's Qakview, 1 Califl, assignor on;oneghalf to- TediG', Rokos, Los Angeles, Calif.

Application: September.- s, 1951, seriama 245,745

7 claims; (01. 74-441) inventionsrelatesls tof.positive; feedsattachment'efor: machinery vsuch;as1 lathes and-fiche.

like Inspiarticulart, the;- invention isicencernedh With.afccuratei-,.positive, ,and;.immediatepositioneingnfzaecuttinectooliwithzrespeet.to awork-piece:

andigthe, prevent-i of? endiplayror; axial play: of

' has sbeenapositionem In: at lathe; .fo r'? example; feed screw on, a

cross-1. slide carriages mayy be;- provided with: one 4 or? more:lecke-nutsi and marries: a tool-holding slideimemherrfomadj ustably; andiseleetivelxi'posie timing-a tool-:- supported. by, the member. withrespect ;toathezmetai1- t0.;-be:;worked-., In iorder to.selectivelyynositien itheicutting tooleit'l-is; in some 1pri'on'proposed arrangements; necessary 130?. ad:-

vancathe v cutting to'ol.slightly zloeyond itsultimate 4-desired-icutting jpositioniandzthen; to "retract the tool-:1so;as'..teztak.e up anygplay or slackibetweenthetool:siiclm-memloenandtheieedscrew.v After.

; itahas: been retracted.- ,to; u1timate position .the;

tQOhSlidGr: member; is; usually-1' locked, in a; 11051-- tionronthefieedmcrewt by, meansof Tone onmore.

lock-1;: nuts) or: other: suitable: means. 7 Itis=-we11,

understood by: those: skilled :in the. art that ,the-

accurate :positi on-ing of; such; aecuttingg tool .re- 1 quiresmot only'famfliaritywitiia 1p articular .ma-.-- chinebutsialsolahighzdegreeqof1skill in accurately-' and. quickly adjusting the cutting:toolHinto-its; final; ultimate cuttinggpositiom If; this,-.adj.ust-

menta isyznotzjproper and end plays in the feeds-- ingzmechanism 51S!not ;eliminated, theetoolr may;

chatter 'rWhembrou-ghteinto;cutting engagement withiea zpiecei aniathe;metal ,.may;be:- inac' curatel-tt." cute to amund'esireduz size; 7 Sincevery,

smalb: differences: maybe: critical it t is. possible. toiirreparablydamageametalpiece being Worked: uponibyn the -pr$SenG8E:0fZa.:-,s1ightamount ofaendr: playi in thelz fee-dingr mechanism Such: a: high;degreezofzaiccuracy required. in wthe..i ultimate posie tioning: Of;the? cutting: tool usually necessitates l spending; considerable; time;iri-oaccuratelyg p.051!" adanted ifor: use zonzlvariousi; types ofmachinery;

suoh'xasatlathenwherebyjaricutting tool may;.be.-

quicklw 'ultimatelyir positioned; without; end tplay,inithe;feedqmechanism.a

Anotherfobjectaof thisjnventionals to -provide meansr;for:preventing;vendwplay betvveen a feed; nutameans sand a-rfeed lserew wherem- 531dfeed nut .meaneand sorewarexcooperahleeto accurate.

lyspositien. a-;;cutting-:-;to01; with, respect to. a werkapiecen YA-,further -:obj.eet of-zthis -invention is" :to designithereforegzanobjection this-. invention ;.to,,- provideia. positive:feed; attachment; which is:

andiprovide azpositive -feedIattachment fori'aute matically preventingiaxial playx'between. as feed screw and a feed nut means wherein amovable nut:- carried by. said: screw: is: movable out ofphasemelationship 2' With' the:- feed' screw} against:

a: feed .nut1so1as; toLeliminate axial play between theL-feed.screWt-and; the :feed nut;

A furtherlobjectiiofzthisjnventionzis to provide: a positivefeedzattachment'iforttmachineryg where; W in .a movable.- nutzis:operable-:ebetweentaa pair? Ofi feed nuts fixed; with; respecti to atooleholding: means .7 and. carrie'diby 'ax feedescrewtwherein at. leastone;end'.fa-ce:1 ofi'the :movable enut is: 0001381?" ableiwithaaniopposed:endtface ref one prime-fixed? nuts:for-;-prevention-;of iel'l'd play.

This 1 invention: contemplates -21; positive automatic feedattachmentiwherein' sides 'of a: mail-"- able nut and opposedendifacesof ai pairioflspaced" v fixed .nutsare providedrwith cooperativeelements for selective engagement' to preventiend play-in"- the .feedattachment Still. another? object of v this invention. is to providevamovable nut" such as described 1 above Which is afforded biased-frictional ineans for en gagementiiwithz aafeed screw.

Generally speaking, this: inventioir-i o'ontem'-= plates :a means f0r"autom'ati'cally preventing end play or? axial play between a=-feedscrew and a. feed: nut means as? provided in the feeding mechanisrnonza cross siidecar ria'g'e-z of a lathe;

ried by a rotatable feed-1 sc'r'eware provided with; opposed innerfaces? A movable nut is threaded on thez-feed ser'ew betweensaidinnerfaces; each v side of 'the amo'vz'tbl nut 'bei-ng-.- nor-'--mallyspaced from: air opposed inner face of the 1, fixed: nuts wherebythe movable nut may be ;rotated;-as:the feed screw is -turned, tomoveaxially toward either one or" the-' other of the feednutsirdepending upon thedi rection of rotationxof theLscreWJ The"opposed sides ofthe movable -nut and the faces' of the ifixed feed nutscarry pairs of cooperative elements" fer limit ingi'axia'l movement 05-'the movable -nut against tit-the threads of a r feed-. nut: in n a;position; the 4- movable nut in out-e phase relationship withi theithreads-otfthei adjacent ieed nut adis tance; of: betweenw 0.03 L and 10:09 of s the-pitc'h of I said threads; Rinse-rotation of the feed screwmayadvance-zandstopa tool-molding slide memberfwith endipl'ay:betweenstherfeed nut means and ;the ;feed screw-automaticallyprevented be? cause: of the enga'gementiof thewcooperative :ele'- withone of thenfix edments of the movable nut Other objects and advantagesof this invention will be readily apparent from the followingdescription of the drawings.

In the drawings:

Fig. 1 is a perspective view of a cross slide carriage for latheembodying this invention.

Fig. 2 is an enlarged fragmentary sectional view taken in a verticalplane indicated by line II-II of Fig. 1.

Fig. 3 is an enlarged exploded perspective view of the position feedattachment illustrated in Fig. 2.

Fig. 4 is a sectional view taken in the plane indicated by line IVIV ofFig. 2.

Fig. 5 is a transverse sectional view taken in the plane indicated byline V--V of Fig. 2.

Fig. 6 is a diagrammatic view showing a phase relationship between thethreads of the fixed feed nuts and the movable nut.

Fig. '7 is an enlarged fragmentary sectional view of the movable nuttaken in a plane passing through the axis of the feed screw shown in.

Fig. 2.

In Fig. 1, a cross slide carriage generally indicated at H) is ofwell-known type for exemplifying the employment of this invention on alathe. The carriage l0 provides a bed I for a tool slide member l2, saidtool slide member. l2 carrying a swivel support generally indicated atl3 for a tool holder generally indicated at M. The tool holder |4 maycarry a cutting tool I5. The specific details of the cross slidecarriage, swivel support, and tool holder have not been shown becausthey are well-known in the art and do not form a part of this invention.The tool slide l2 may be moved longitudinally of carriage l0 upon bed Hby rotating a feed handle l6 which may be connected to a feed screw IIin usual manner.

Th feed screw may be, journaled at opposite ends in carriage ID asillustrated in Fig. 2 at l8 and IS. The tool slide member |2 may beprovided with a feed nut means 26 which may depend downwardly from theslide within an elongated opening in the carriage for threadedcooperation with feed screw ll so that as handle I6 is turned, thethreaded engagement between feed screw I1 and feed nut means willadvance or retract the tool slide member |2. feed nut means isillustrated as being integral with the tool slide member, it isunderstood that the feed nut means may be attached to the tool slidemember in any suitable manner.

Th feed nut means 20 comprises a pair of spaced feed nuts 2| and 22,each nut 2| and 22 having threaded engagementwith the feed screw II. Thethreads of the feed screw may be of square or acme type, each threadhaving a front face 23 and a rear face 24. The feed nuts 2| and 22 haveopposed parallel faces 25 and 26 lying in planes transverse to the axisof the feed screw.

Between the faces 25 and 26 of feed nuts 22 and 2| respectively, thereis provided a movable nut 21 having internal threads 28 of the samepitch as the threads of feed nuts 2| and 22. Preferably, although notnecessarily, the feed nut means may be formed by drilling and threadinga borev through a solid block of metal. After threading,

an inner section may be cut out of the block so as to form the twospaced connected feed nuts 2| and 22. The movable nut 21 may be formedfrom the cut-out section and provided with a circular peripheral edgepermitting rotation of the nut on 13:51; feed screw between the feednuts 2| and Each face 25 and 26 is provided with a pair of While the Ydiametrically opposed wedge elements 29 and 30 respectively, said wedgeelements having arcuate inclined pairs of wedge faces 3| and 32 respec--tively. Each pair of wedge faces 3| and 32 are inclined in a directionopposite to the pitch of the thread of the feed screw. It should benoted that elements 29 are disposed in angular relationship to theelements 30, in the example shown approximately On opposite sides themovable nut 21 is provided with inclined arcuate diametrically oppositepairs of wedge faces 33 and 34, the pair of wedge faces ,33 being on theside of the nut 27 facing wedge elements 29, and the wedge faces 34being on the side ofthe nut facing the wedge elements 36. The pairs ofwedge faces 33 and 34 are likewise disposed in angular relationship toeach other, in the example shown, of approximately 90, so as tocooperate with the respective faces 3| and 32 on the feed nuts.

The pairs of wedge faces 33 and 34 on movable nut 21 may be formed onsaid nut at an intermediate point between the elements 29 and 3|] whenthe nut is'in phase relationship with the threads of feed screw that iswhenthe nut is in the original position of the cut-out section when theblock was initially threaded.

In operation, when the tool slide handle I6 is rotated clockwise so asto move the tool slide forwardly or into the machine, the feed screwwill cause the feed nut means to advance to the left as viewed in Fig.2. As the feed nuts begin to advance along the threads, the movable nutis rotated clockwise by reason of its frictional contact with thethreads of the feed screw. Such rotation of the movable nut 21 bringsthe wedge faces 34 on th nut 21 into Wedge engagement with the Wedgefaces 32 of elements 36 provided on the face 26 of the feed nut 2| andaxial movement of the nut 2|is stopped. Such wedge engagement forces themovable nut-21 out of phase relationship with the threads of the feedscrew l1 so that end play or relative axial movement between the feednut means and the feed screw I1 is eliminated. Thus, the tool slidemember I2 is advanced and held without any slack bein present in thethreaded attachment of the tool slid with the feed screw Suchout-of-phase relationship is diagrammatically indicated in Fig. 6wherein the solid line 36 represents the path of the thread of the feedscrew Normally, when a nut is in phase relationship with such a path 36,the path of its thread lies coincident with line 36, clearance beingprovided between the threads of the screw and nut. When the movable nut21 is rotated by the feed screw against a feed nut, the path of thethreads of the movable nut move out of phase relationship with thethreads of the feed nuts and are held out of phase by the pairs ofcooperative elements 23, 30 and th wedge faces 33, 34. The path of thethreads of the movable nut is represented by the dotted line 37. Axialplay is elimi nated because the clearance between the threads of thescrew and the feed nuts in a longitudinal direction has been virtuallyeliminated. Stop ping axial movement of the movable nut toward theadjacent feed nut by the cooperative elements on the feed nuts andmovable nut positions the threads of the movable nut out of phase withthe threads of the feed nuts by a distance of between about 0.03 and0.09 of the pitch of said threads.

In order thatthe movable nut 21 may positively move or turn with therotation of the feed screw H, in Fig. 7 I have illustrated a frictionalfrictionarmaterialsuch as a composition-fiber; I

a spring to having one end seated-on said cap and -the otlier end seatedon a set screw 4|. The set screw Al may be adjusted so that the spring49 is compressed" to any -desired degree for preselected frictionalengagement of cap 39 with the crest of the threads of the feed screw ll.

It will be understood, of course, that the cooperative engagement of themovable nut and the feed nuts will provide a positive feed without theuse of the auxiliary frictional means of Fig. 7. Friction between thethreads of the movable nut and screw is usually suflicient to cause themovable nut to turn so as to move against a feed nut.

The cooperative wedge elements and wedge faces on the feed nuts andmovable nuts respectively acting along inclined surfaces directedoppositely to the direction of advancement of the threads of the feedscrew quickly and positively move the threads of the movable nut out ofphase with the threads of the feed nuts and hold them out of phase.Release or return of the movable nut to in-phase relation isalso quicklyaccomplished when the feed handle is rotated counterclockwise. As thehandle is further rotated, the cooperative elements on the other side ofthe movable nut and adjacent feed nut coact to again move the movablenut out of phase with the feed nut and end play is eliminated.

Those skilled in the art will note'that a tool slide member may thus beaccurately, positively, and quickly moved to a preselected position andthat any end play or relative axial movement between the feed nut meansand the feed screw has been automatically eliminated.

All changes and modifications of the positive feed attachment describedabove coming within the scope of the appended claims are embracedthereby.

I claim:

1. Means for automatically preventing end play between a feed screw anda feed nut comprising: a rotatable feed screw restrained from axialmovement and. provided with threads having a forward face and a rearface; a pair of spaced feed nuts, each provided with an internallythreaded bore, said bores being in alignment and arranged to threadedlyreceive the rotatable feed screw, each of said feed nuts having an endwall in spaced, opposed and unchanging relation to the end wall of theother feed unit; a movable nut rotatably and threadedly carried by thefeed screw between said feed nuts, the ends of said movable nut beingnormally spaced from the opposing end walls of the feed nuts wherebysaid movable nut may be rotated to move axially toward either of thefeed nuts; means carried by the movable nut to frictionally grasp thefeed screw; and cooperative elements carried by the ends of the movablenut and the opposing end.

wall of the adjacent feed nut for stopping axial movement of the movablenut toward such adjacent feed nut with the threads of the movable nutout of phase with the threads of said adjacent feed nut a distance ofbetween about 0.03 and 0.09 of the pitch of such threads.

2. A device of the character stated in claim 1 wherein the cooperativeelements include faces 6* inclined-:1imazdirectiorrz oppfisitez: tor thepitch, of

saidKfeed-Iscrew:

3'? Meanseforautomaticallypreventing endiplay betweerra feed sorew; and'a-s feednut comprising: a rotatable-- fe'ed screw restrained from axialmovementwand provided wi-tli' threads having. a v forward-face and a'rear race;- a pair of spaced 1 feednuts, eachprovided; withaninternally threadedbore; said boresab'eing in alignment and:arranged-to threadedly receive 1 the rotatable feed' screw; eachbfFsaid-TIeed nutsliaVing amend wall in spaced, opposed and unchangingrelation to the end wall of the other feed nut; a movable nut rotatablyand threadedly carried by the feed screw between said feed nuts, theends of said movable nut being normally spaced from the opposing endwalls of the feed nuts whereby said movable nut may be rotated to moveaxially toward either of the feed nuts; and cooperative elements carriedby the ends of the movable nut and the opposing end wall of the adjacentfeed nut for stopping axial movement of the movable nut toward suchadjacent feed nut with the threads of the movable nut out of phase withthe threads of said adjacent feed nut a distance of between about 0.03and 0.09 of the pitch of such threads.

4. Means for automatically preventing end play between a feed screw anda feed nut comprising: a rotatable feed screw; a pair of spaced feednuts, each provided with an internally threaded bore,

' said bores being in alignment and arranged to threadedly receive therotatable feed screw, each of said feed nuts having an end wall inspaced, opposed and unchanging relation to the end wall of the otherfeed nut; a movable nut rotatably and threadedly carried by the feedscrew between said feed nuts, the ends of said movable nut beingnormally spaced from the opposing end walls of the feed nuts wherebysaid movable nut may be rotated to move axially toward either of thefeed nuts; and cooperative elements carried by the ends of the movablenut and the opposing end wall of the adjacent feed nut forstopping'axial movement of the movable nut toward such adjacent feed nutwith the threads of the movable nut out of phase with the threads ofsaid adjacent feed nut a distance of between about 0.03 and 0.09 of thepitch of such threads.

5. Means for automatically preventing end play between a feed screw anda feed nut comprising: a rotatable feed screw; a pair of spaced feednuts, each provided with an internally threaded bore, said bores beingin alignment and arranged to threadedly receive the rotatable feedscrew, each of said feed nuts having an end wall in spaced, opposed andunchanging relation to the end wall of the other feed nut; a movable nutrotatably and threadedly carried by the feed screw between said feednuts, the ends of said movable nut being normally spaced from theopposing end walls of the feed nuts whereby said movable nut may berotated to move axially toward either of the feed nuts; and cooperativeelements carried by the ends of the movable nut and the opposing endwall of the adjacent feed nut for stopping axial movement of the movablenut toward such adjacent feed nut.

6. A device of the character stated in claim 5 wherein the cooperativeelements on the movable nut and the adjacent feed nut are respectivelydiametrically arranged and are normally angularly displaced when themovable nut and feed the feed nuts whereby said movable nut may berotated to move axially toward either of the feed nuts; andccoperativeinclined faces carried by the ends of the movable nut and theopposing end wall of the adjacent feed nut for stopping axial movementof the movable nut toward such adjacent feed nut.

MICHAEL P. ROKOS.

No references cited.

